i have a weil mclain pd8 boiler, about 2 weeks ago it failed to work and would not fire. I turned the valve on the end of the gas valve to manual and it lit. I then turned it back to auto and it stayed lit and functioned properly since. I did it again after two weeks. I again moved the valve to manual but this time it wsould not stay lit when turned back to auto. I spent that evening cycling it this way to keep the house warm. well, one time i did not get back to it soon enough and it blowed off the overpressure valve with LOTS of steam. I shut it down and suffered through a cold night. Since then I determined that the pressure reducer wasn't functioning and the pop off valve was seeping, after replacing both of these and refilling and bleeding the system. It wont burn, I replaced the thermostat thinking maybe that was the problem and now sometimes the thermostat will start it and sometimes it won't. Seems like I will get on good cycle then it wont restart. Any ideas?

I have a baseboard heating system with an old Weil-McLain PC-G 6 Series 4 gas boiler. Recently had the pipes bled and soon after noticed a load banging sound coming from the boiler that echoed through the pipes. It was most noticeable when the system fired up from a period on prolonged inactivity. After checking for various causes on the web, self diagnosed that it might still be air in the system. Since I no longer heard the sound of rushing water in the pipes I assumed they were properly bled. Saw a posting about opening an air vent to release air in a heating system and decided to give that a try. I unscrewed the cap of the "tire type" air vent on top of the furnace and depressed the valve until water started seeping/dripping out. The air vent is an American Tube and Connector Series 700 (appears older) and the label states that for proper functioning, the cap must be unscrewed at least two times. I followed the advice, but water continues to drip out slowly from the valve. There was some scale and mineral deposits on the top of the vent, so it looks like it had leaked in the past. Am I OK just tightening the valve cap all the way and leaving it "closed" completely to stop the leak? The banging noise appears to have been quieted, so I'm hoping I don't need to replace the air vent just yet.